This invention relates generally to probes for detecting radiation, and more particularly to collimating probes for detecting, localizing, and imaging or mapping of radiation in biological systems or other systems.
The use of radioactive materials to tag tissue within a patient for effecting its localization and demarcation by radiation detecting services has been disclosed in the medical literature for at least forty years. Significant developments in the localization and demarcation of tissue bearing radioactive isotope tags for diagnostic and/or therapeutic purposes have occurred since that time. Thus, it is now becoming an established modality in the diagnosis and/or treatment of certain diseases, e.g., cancer, to introduce monoclonal antibodies tagged with a radioactive isotope (e.g., Iodine 125) into the body of the patient. Such monoclonal antibodies tend to seek out particular tissue, such as the cancerous tissue, so that the gamma radiation emitted by the isotope can be detected by some apparatus, e.g., a MRI or CAT scanner, to provide information and/or an image of the radiation emitting tissue.
As is known MRI and CAT scanning apparatus are extremely large, and thus not suitable for use in an operating room. Thus, while the surgeon may be able to utilize some hard copy image or data regarding the radioactively tagged tissue provided by an MRI or CAT scanner during the surgical procedure the surgeon will, nevertheless, want to manually explore various possible sites that may contain cancerous tissue to ensure that no such tissue has been overlooked or missed. Such action is typically accomplished visually and/or by palpation. Obviously, such inspection procedures are complicated by the limited amount of time available to the surgeon during the surgery, the type of cancer involved, and its possible location(s).
One type of apparatus which is small enough to be used in the operating room to assist the surgeon in detecting and localizing the presence of radioactively tagged tissue within the body of the patient makes use of a hand held radiation detecting probe. Such a probe is disposed or held adjacent portion of the patient's body where the cancerous tissue is suspected to be in order to detect if any radiation is emanating from that site, thereby indicating that cancerous tissue is likely to be found there. Unfortunately, radiation from the tagged tissue scatters off of the various surrounding body tissues organs, thereby rendering the localization of the source of the radiation difficult. Much of the indium 111 monoclonal antibody accumulates non-specifically in the liver.
One technique for localizing the radiation source is to look for the highest energy rays emanated by the radioactive isotope. This technique is based on the theory that the lower energy rays received by the probe must have undergone some scattering, whereas the higher energy rays remaining could not have undergone such scattering and must be coming from a source directly in front of the probe. While that technique has some merit it does not work well for all types of isotopes.
An alternative approach to localize the source of radiation is to utilize some device with the probe so that the surgeon or operator of the device can adjust the solid angle (cone) in which radiation can be received or accepted by the probe's detector. One such probe and associated device is commercially available from Neoprobe Corporation under the designation Neoprobe 1000. That probe makes use of three collimators, each of which can be attached in either an extended or retracted position on the probe to establish a minimum and maximum solid angle from which radiation can be detected. In particular, each of the Neoprobe 1000's collimators is a device having a different size small diameter opening which is arranged when secured to the probe in the extended position (so that its narrow diameter provides a constrained or narrowed field, i.e., the minimum solid angle of acceptance) to localize the radiation source within a small area. When the collimator is retracted or removed the solid angle of acceptance is maximum, and thus the area from which the radioactivity can be detected is significantly larger. Thus, it is suggested that when using the Neoprobe 1000 that the collimator be removed or retracted for wide angle scanning (e.g., broad survey use), and that the collimator be connected and extended for localized scanning.
In our copending U.S. Pat. Application Ser. No. 07/363,243, filed on June 8, 1989, U.S. Pat. No. 4,959,547 entitled Apparatus and Methods for Detecting, Localizing and Imaging of Radiation in Biological Systems, whose disclosure is incorporated by reference herein, and which is assigned to the same assignee as this invention, there is disclosed a collimating probe which overcomes many of the disadvantages of prior art collimating probes. In particular that probe comprises a radiation detector and an adjustment mechanism for adjusting the solid angle through which radiation may pass to the detector. That solid angle is continuously variable. The probe is constructed so that the only radiation reaching the detector is that which is within said solid angle. By adjusting the solid angle from a maximum to a minimum while moving the probe adjacent the source of radiation and sensing the detected radiation one is able to precisely locate the probe at the source of radiation. The probe can be used for diagnostic or therapeutic purposes. A receptacle is also provided to hold a specimen on the probe to detect the presence of radiation emanating therefrom.
In U.S. Pat. No. 4,801,803 (Denen et al) assigned to Neoprobe Corporation there is disclosed a probe having a distal end arranged to have a separate collimator mounted thereon to provide the probe with a higher directional aspect. The collimator for achieving that end is not shown nor described. Means are, however, shown and described for mounting the collimator to the probe. Such means comprises a first retainer groove 42 extending about the periphery of the probe's distal end, and a second retainer groove 102 disposed closely adjacent the groove 42 and formed by the edge of a shell 66 and a wall portion of the distal end of the probe when the shell 66 is disposed thereon.
The following U.S. patents relate to collimators and/or apparatus for use with x-ray or other radiation detecting equipment, e.g., x-ray machines, etc: 3,112,402 (Okun et al.), 3,310,675 (Prickett et al.), 3,628,021 (MacDonald), 3,609,370 (Peyser), 3,869,615 (Hoover et al.), 3,919,519 (Stevens), 3,936,646 (Jonker), 4,340,818 (Barnes), 4,419,585 (Strauss et al.), 4,489,426 (Grass), and 4,502,147 (Michaels).
In some applications, like the aforementioned Neoprobe prior art devices, it may be desirable or expedient to utilize a separate collimator for securement to the probe to reduce the probe's normal solid angle of acceptance. In such a case a need exists for a probe and associated collimator which are constructed so that the collimator can be readily releasably secured to the probe by means which are simple, reliable, and efficient. Moreover, probes constructed in accordance with the teachings of our aforementioned patent applications may also make use of a separate releasably securable collimator constructed in accordance with the teaching of this invention. Further still collimators may be constructed in accordance with this invention which can be releasably mounted on a probe in one of several selected positions to adjust the solid angle of acceptance to predetermined values.